[Otogenic cavernous sinus thrombophlebitis. A case report]

OBJECTIVES

Acquire knowledge concerning the diagnosis and treatment of otogenic cavernous sinus thrombophlebitis.

PATIENT AND METHODS

We report a case of otogenic cavernous sinus thrombophlebitis (CST) in a 6-year-old boy.

RESULTS

CST diagnosis was based on clinical signs (septic illness, ocular nerve palsy and chemosis), and neuro-imaging confirmed the diagnosis. Contrast-enhanced CT scan demonstrates different signs: (i) filling defect or heterogeneous enhancement of cavernous sinus, (ii) cavernous sinus enlargement with bulging of the lateral wall, (iii) intensive enhancement of lateral wall corresponding to enhancement of a collateral network replacing the thrombosed cavernous veins, (iiii) and sometimes indirect orbital signs (exophthalmus, densification of the retro-orbital fat, superior ophthalmic dilatation with partial or no enhancement in case of thrombosis extension). The bacteria most frequently found are Streptococci, Streptococcus pneumoniae, Staphylococcus aureus, Gram-negative rods and anaerobes combined. The therapeutic management of CST consists of intravenous administration of appropriate antibiotics combined radical mastoidectomy if medical therapy has failed. Anticoagulant therapy is controversial.

CONCLUSION

Knowledge of early diagnosis of otogenic cavernous sinus is important because prior to the antibiotic era, CST was almost always fatal. Currently, therapeutic outcome is not always favorable due to high morbidity after aggressive treatment.

Expression and G-protein coupling of mu-opioid receptors in the spinal cord and dorsal root ganglia of polyarthritic rats

Although chronic inflammatory pain is known to be associated with hypersensitivity to mu opioid receptor agonists, no evidence for changes in the expression and/or characteristics of central mu opioid receptors has yet been reported in relevant models of this type of pain. In the present study, both immunohistochemical and autoradiographic approaches were used to address this question in polyarthritic rats, on the 4th week after intradermal injection of complete Freund's adjuvant, when inflammatory pain was at its maximum. Immunohistochemical labeling with specific anti-mu opioid receptor antibodies and autoradiographic labeling with [3H]DAMGO showed an upregulation of mu opioid receptors in the dorsal root ganglia but no changes in the density of these receptors in the dorsal horn at the level of L4-L6 segments in polyarthritic compared to age-paired control rats. On the other hand, autoradiographic quantification of the concentration-dependent increase in [35S]GTP-gamma-S binding by the mu-opioid receptor agonist DAMGO did not show any significant differences within the lumbar dorsal horn between polyarthritic and control rats. These data indicate that chronic inflammatory pain caused by polyarthritis was associated with an increased expression of mu-opioid receptors in dorsal root ganglion sensory neurones that did not result in an increased spinal density of these receptors, in spite of their well established axonal transport in the central portion of primary afferent fibres to the dorsal horn. In contrast, axonal transport of mu-opioid receptors in the peripheral portion of these fibres probably accounts for the increased receptor density in inflamed tissues already reported in the literature.

Dihydroergotamine and its metabolite, 8'-hydroxy-dihydroergotamine, as 5-HT1A receptor agonists in the rat brain

1 In addition to stopping migraine attacks, dihydroergotamine (DHE) is an efficient drug for migraine prophylaxis. Whether 5-HT(1A) receptors could contribute to the latter action was assessed by investigating the effects of DHE and its metabolite, 8'-OH-DHE, on these receptors in the rat brain. 2 Membrane binding assays with [(3)H]8-OH-DPAT and [(3)H]WAY 100635 as radioligands showed that both DHE (IC(50)=28-30 nM) and 8'-OH-DHE (IC(50)=8-11 nM) are high-affinity 5-HT(1A) receptor ligands. 3 Both DHE and 8'-OH-DHE enhanced the specific binding of [(35)S]GTP-gamma-S to the dorsal raphe nucleus and the hippocampus in brain sections, but to a lower extent than 5-carboxamido-tryptamine (5-CT) in the latter area. 4 Both DHE (EC(50)=10.9+/-0.3 nM) and 8'-OH-DHE (EC(50)=30.4+/-0.8 nM) inhibited the firing of serotoninergic neurons in the dorsal raphe nucleus within brain stem slices. 5 Intracellular recording showed that 8'-OH-DHE was more potent than DHE to hyperpolarize CA1 pyramidal cells in rat hippocampal slices. 6 Both the stimulatory effects of DHE and 8'-OH-DHE on [(35)S]GTP-gamma-S binding and their electrophysiological effects were completely prevented by the selective 5-HT(1A) receptor antagonist WAY 100635. 7 As expected of 5-HT(1A) receptor partial agonists, DHE and 8'-OH-DHE prevented any subsequent hyperpolarization of CA1 pyramidal cells by 5-HT or 5-CT. 8 Through their actions at 5-HT(1A) auto- (in the dorsal raphe nucleus) and hetero-(notably in the hippocampus) receptors, DHE, and even more its metabolite 8'-OH-DHE, can exert both an inhibitory influence on neuronal excitability and anxiolytic effects which might contribute to their antimigraine prophylactic efficiency.

[Mechanisms of action of antidepressants: new data from Escitalopram]

A first improvement in the treatment of depression was achieved in 1970-80 with the development of selective serotonin reuptake inhibitors (SSRI) because these drugs, which are as potent antidepressants as the tricyclics, are devoid of most of the secondary effects of the latter drugs (orthostatic hypotension, weight gain, dry mouth, etc, mainly caused by their capacity to block alpha1-adrenergic, H1 histaminergic and muscarinic receptors). However, SSRI did not solve all the problems inherent to the treatment of depression because (i) approximately 30% of depressed patients do not respond to these drugs, and (ii) their antidepressant effect becomes really significant only after 3-4 weeks of treatment, like that observed with tricyclics. A further improvement in the development of antidepressant drugs has recently been made with the synthesis of the S enantiomer of citalopram, called Escitalopram. Indeed, this active enantiomer is the most selective among all SSRI available to date, including citalopram. In addition, the potency of Escitalopram to inhibit serotonin reuptake (K(i)=2,1 nM) and to induce antidepressant-like effects in relevant animal paradigms (forced swimming test; chronic mild stress; stress-induced ultrasonic vocalization) is markedly increased as compared with citalopram and other SSRI. In particular, in the forced swimming test, which is especially relevant for assessing the potential antidepressant properties of drugs, Escitalopram was shown to be at least 15 fold more potent than any other SSRI to delay helplessness-induced immobility of rats. Even more interestingly, under chronic treatment conditions, Escitalopram was found to be significantly more rapid than any other antidepressant (tricyclics such as imipramine, SSRI such as fluoxetine) to restore sucrose intake in rats subjected to chronic mild stress, suggesting a reduced delay in its antidepressant action. This was indeed fully confirmed in humans as only 1-2 weeks of treatment with Escitalopram was enough to significantly reduce MADRS score in depressed subjects, compared to 3-4 weeks with any other antidepressant drug. These unique properties led to further investigations of the pharmacological profile of Escitalopram. It thus appeared that, at equipotent doses, the S enantiomer was significantly more efficient than citalopram (racemate) to increase the extracellular levels of serotonin within the frontal cortex of freely moving rats bearing a locally implanted microdialysis probe. Further experiments showed that R-citalopram counteracted the capacity of Escitalopram to enhance extracellular 5-HT levels, thereby explaining why the racemate had only a limited action in this regard. In addition, behavioural studies (stress-induced ultrasonic vocalization test) also showed that R-citalopram exerts effects opposite to those (antidepressant--and anxiolytic--like effects) of Escitalopram. The reason for these differences between the two enantiomers might concern the secondary molecular targets at which citalopram acts, but with affinities at least two orders of magnitude less than for the serotonin transporter. Indeed, R-citalopram has a 7-10-fold higher affinity for H1 histaminergic (K(i)=180 nM) and alpha1-adrenergic (K(i)=560 nM) receptors than Escitalopram (respective K(is) > or = 2 000 nM), and this difference might contribute not only to the better selectivity of the latter enantiomer for its therapeutically relevant target (i.e. the serotonin transporter) but also to its improved capacity to enhance central 5-HT neurotransmission. On the other hand, the global affinity of Escitalopram (K(i)=200-430 nM) for both subtypes of sigma receptors (sigma1 and sigma2) is higher than that of R-citalopram (and of the racemate citalopram; K(i)=200-1 500 nM), and this might also strengthen the antidepressant and anxiolytic effects of the S enantiomer because behavioural studies showed that selective sigma1 and sigma2 agonists are endowed with both antidepressant--and anxiolytic-like properties in relevant animal models. However, to date, the exact nature (agonist or antagonist) of the action of Escitalopram at sigma receptors is not known yet, and this question has to be addressed in future investigations. Altogether, these data open novel perspectives for both a better treatment of depressive disorders and a better knowledge of the neurobiological mechanisms underlying antidepressant therapy, and, possibly, depression itself.

Effects of genetic depletion of monoamines on somatosensory cortical development

Raised levels of serotonin cause alterations in the development of the barrelfield of the primary somatosensory cortex (S1) in rodents. We examined the development of S1 in genetic mouse models in which the levels of serotonin and/or dopamine and noradrenaline are drastically reduced. Mice lacking the vesicular monoamine transporter type 2 (VMAT2 KO) are hypomorphic with rare pups surviving until postnatal day (P) 6. Serotonin, dopamine and noradrenaline are almost undetectable in the brain. In S1 we find that the segregation of thalamocortical axons into whisker patterns is delayed by 1 day and that layer IV granular neurons fail to form normal barrels. Moreover, the growth of cortical layers II-IV is reduced. Despite severe malnutrition, we show that these alterations are not caused by increased cell death in the thalamus or S1. Moreover, the maturation of cortical neurons is not altered as reflected by calcium-binding protein immunolabeling. Mice lacking both VMAT2 and monoamine oxidase type A (MAOA) were generated. VMAT2-MAOA DKO mice are hypomorphic but survive until P13. Increased levels of serotonin but profoundly reduced dopamine and noradrenaline levels are found in the brains. In S1, alterations are similar to those observed in MAOA KO mice: thalamocortical axons and granular neurons failed to form barrels. In addition there is a severe reduction in the thickness of the upper cortical layers as in the VMAT2 KO mice. These results show that monoamines have no instructive effect per se on the formation of thalamocortical patterning in S1. However, monoamines appear to be essential for the normal cytoarchitectonic maturation of the granular (IV) and supragranular cortical layers (II-III). Since developmental cell death and chemoarchitectonic differentiation of these neurons are not modified, it is possible that these alterations result from migration defects and/or from altered synaptic maturation.

Pre-operative balloon counterpulsation and off-pump coronary surgery for high-risk patients

Coronary artery bypass surgery (CABG) can be performed less invasively without cardiopulmonary bypass (CPB). Multivessel off-pump CABG (OPCAB) is challenging in patients with critical left main stenosis (> 70%) and/or severe ventricular dysfunction (ejection fraction < 0.35) Our objective was the evaluation of efficiency of intra aortic balloon pump (IABP) preoperatively in this high-risk group in order to perform OPCABG safely.

MATERIAL AND METHOD

In a consecutive 10-month period (out of 88 OPCABG patients) 23 high-risk patients were treated and were compared with 15 on-pump patients (out of 69) with the same criteria.

RESULTS

Preoperative implantation of IABP was significantly higher in the OPCABG group (70% vs 46%, p < 0.05). No conversion to CPB was required in the OPCABG group. Post-operative angiography was systematically performed and demonstrated 97.5% patency of anastomosis. No device-related complications occurred. No difference was found concerning age, risk factors, emergency surgery, ejection fraction, mean number of grafts per patient (2.64 versus 2.75) and average operating time. In contrast, OPCABG demonstrated a trend toward reduced morbidity in terms of atrial fibrillation, reexploration for bleeding and prolonged ventilator requirement > 12 h. Mortality was less in the OPCABG group (p < 0.05).

CONCLUSION

More randomized controlled trials are needed to evaluate the true efficacy of elective IABP in OPCABG high-risk patients. Until such studies are evaluated, and therefore because older and sicker patients now constitute a greater percentage of candidates for OPCABG, the timing of application of the IABP is warranted. These results may further justify preoperative use of the IABP in a large proportion of this group of patients.

Prospective evaluation of the effect of an angiotensin I converting enzyme gene polymorphism on the long term risk of major adverse cardiac events after percutaneous coronary intervention

OBJECTIVE

To evaluate prospectively the influence of an angiotensin I converting enzyme (ACE) gene polymorphism on long term clinical outcome of patients with established coronary artery disease treated by percutaneous coronary intervention.

DESIGN AND SETTING

Prospective observational study in a university hospital.

PATIENTS

Consecutive series of 1010 patients with symptomatic coronary artery disease who underwent successful coronary stent placement from November 1996 to April 1998.

MAIN OUTCOME MEASURES

Long term clinical outcome was obtained and the rates of major adverse cardiac events (death, non-fatal acute myocardial infarction, unstable angina, and revascularisation) were compared according to the insertion/deletion (I/D) polymorphism of the ACE gene.

RESULTS

Of the 1010 patients 29% had the DD genotype, 51% had the ID genotype, and 20% had the II genotype. All baseline clinical angiographic and procedural characteristics were identical in the three groups of patients. Event-free survival during the follow up period (median two years) was identical in patients with the II genotype compared to those with one or two D alleles. The predictors of long term survival were age, diabetes, ejection fraction, and extension of coronary artery disease. ACE genotype had no influence on the long term survival. Additional analyses assuming dominant and recessive effects of the D allele also failed to find any association; nor did the examination of low risk subgroups.

CONCLUSIONS

The ACE I/D polymorphism does not influence the long term prognosis of patients with coronary disease treated by percutaneous coronary intervention, and screening patients for this gene polymorphism is not useful for secondary prevention strategies.

Large intracoronary thrombi with good TIMI flow during acute myocardial infarction: four cases of successful aggressive medical management in patients without angiographically detectable coronary atherosclerosis

Four cases of young patients with acute myocardial infarction are discussed in which urgent angiography showed large intracoronary thrombus and TIMI (thrombolysis in myocardial infarction) flow > or = 2 in the infarct related artery. The rest of the coronary tree appeared to be free of detectable atherosclerosis. Percutaneous transluminal coronary angioplasty was not performed and an aggressive antiplatelet/anticoagulant treatment was administered (acetylsalicylic acid, clopidogrel, abciximab, and heparin). In all cases early angiographic control (1-12 days after AMI) showed disappearance of thrombus, no significant residual stenosis, and normal flow. No deterioration of left ventricular function was observed and the clinical course both in hospital and at five months' follow up was uneventful.

Serotonin(3) receptor stimulation in the nucleus tractus solitarii activates non-catecholaminergic neurons in the rat ventrolateral medulla

The present study was performed to determine whether or not the increased arterial pressure triggered by 5-HT(3) receptor stimulation in the nucleus tractus solitarii and underlain by a sympathoexcitation is associated with the activation of ventromedullary cells known to be involved in vascular regulation, i.e. the C1 and A1 catecholaminergic cells. For this purpose, double immunohistochemical labeling for tyrosine hydroxylase and c-fos protein was performed all along the ventrolateral medulla after microinjection of 1-(m-chlorophenyl)-biguanide, a selective and potent 5-HT(3) receptor agonist, into the nucleus tractus solitarii of alpha-chloralose/urethane-anaesthetized rats. This treatment produced a significant elevation of arterial pressure ( approximately +35 mm Hg). Concomitantly, a significant increase in the number of c-fos expressing neurons was observed in the rostral ventrolateral medulla (+63%), in particular in its most anterior part (+78%), and in the medullary region surrounding the caudal part of the facial nucleus (+91%). Retrograde labeling with gold-horseradish peroxidase complex showed that at least some of these activated c-fos expressing cells project to the spinal cord. However, the number of double-stained neurons, i.e. c-fos and tyrosine hydroxylase positive neurons, did not increase at any level of the ventrolateral medulla. In contrast, under the same alpha-chloralose/urethane anesthesia, systemic infusion of sodium nitroprusside appeared to produce a hypotension and a marked increase in the density of such double c-fos and tyrosine hydroxylase expressing cells in the rostral ventrolateral medulla and the caudal medullary region surrounding the caudal part of the facial nucleus. These data indicate that medullary catecholaminergic C1 and A1 neurons are not involved in the pressor effect elicited by 5-HT(3) receptor stimulation in the nucleus tractus solitarii. However, this 5-HT(3) receptor-mediated effect is clearly associated with the excitation of (non-catecholaminergic) neurons within the pressor region of the ventral medulla.

[The three-dimensional spiral scanner and volume rendering technique: importance in craniofacial traumatology and reconstructive surgery]

There are two reconstruction methods for 3D imaging with a helical scanner: a surface rendering process providing a 3D-SSD (Surface Shaded Display) image that looks like a plaster cast skull and 3D-VRD (Volume Rendering Technique) which is more precise and gives 3D images similar to radiographs. We review briefly the techniques used to acquire these images and present 3D volume-rendering scanners, pointing out its usefulness in craniomaxillofacial traumatology and reconstructive surgery.

5-HT(2A) gene promoter polymorphism as a modifying rather than a vulnerability factor in anorexia nervosa

The A allele of the 5-HT(2A) gene (-1438A/G polymorphism) has been associated with anorexia nervosa in four studies, but not in three others. One possibility to explain such a discrepancy is that the A allele acts as a modifying rather than a vulnerability allele. To test this hypothesis, we increased our initial sample of 102 trios left open bracket Mol. Psychiatry 7 (2002) 90 right open bracket with 43 new patients with anorexia nervosa and 98 healthy controls. In addition to confirming the absence of association on the global sample of 145 patients, we found that patients with the A allele had a significantly later age at onset of the disease (P = 0.032). Furthermore, the A allele was also transmitted with an older age at onset (P = 0.023) using a quantitative-trait TDT approach. The A allele may thus act as a modifying factor (delaying onset), potentially explaining variations of allele frequency across samples, in which differences in average age at onset are not only possible, but also expected. Taking into account vulnerability genes, but also genes modifying the expression of the disorder, will help to disentangle the complexity of the etiological factors involved in anorexia nervosa.

[Rotational vertebro-basilar insufficiency secondary to a fibrous band of the longus colli muscle: value of CT spiral angiography diagnosis]

A CASE REPORT

The authors report a case of rotational vertebro-basilar insufficiency causing "drop-attacks". To our knowledge, it is the first case of extraluminal vertebral artery compression caused by a fibrous band of the longus colli muscle, demonstrated by spiral computed tomographic angiography with volume rendering reformation.

Altered regulation of the 5-HT system in the brain of MAO-A knock-out mice

Genetic deficiency of monoamine oxidase-A (MAO-A) induces major alterations of mood and behaviour in human. Because serotonin (5-HT) is involved in mood regulation, and MAO-A is responsible for the catabolism of 5-HT, we investigated 5-HT mechanisms in knock-out mice (2-month-old) lacking MAO-A, using microdialysis, electrophysiological, autoradiographic and molecular biology approaches. Compared to paired wild-type mice, basal extracellular 5-HT levels were increased in ventral hippocampus (+202%), frontal cortex (+96%) and dorsal raphe nucleus (DRN, +147%) of MAO-A mutant mice. Conversely, spontaneous firing rate of 5-HT neurons in the DRN (recorded under chloral hydrate anaesthesia) was approximately 40% lower in mutants. Acute 5-HT reuptake blockade by citalopram (0.2 and 0.8 mg/kg i.v.) produced a much larger increase in extracellular 5-HT levels (by approximately 4 fold) and decrease in DRN neuronal firing (with a approximately 4.5 fold decrease in the drug's ED50) in MAO-A knock-out mice, which expressed lower levels of the 5-HT transporter throughout the brain (-13 to -34% compared to wild-type levels). The potency of the 5-HT1A agonist 8-OH-DPAT to produce hypothermia and to reduce the firing of DRN serotoninergic neurons was significantly less in the mutants, indicating a desensitization of 5-HT1A autoreceptors. This was associated with a decreased autoradiographic labelling of these receptors (-27%) in the DRN. Altogether, these data indicate that, in MAO-A knock-out mice, the enhancement of extracellular 5-HT levels induces a down-regulation of the 5-HT transporter, and a desensitization of 5-HT1A autoreceptors which allows the maintenance of tonic activity of 5-HT neurons in the DRN.

Differential subcellular localization of the 5-HT3-As receptor subunit in the rat central nervous system

Following the cloning and sequencing of the A subunit of the 5-HT3 receptor, two alternatively spliced isoforms, 5-HT3-AS and 5-HT3-AL, have been identified. In order to analyse the distribution of the receptor, a polyclonal antibody has been produced against the short form which is the most abundant in the central nervous system [Doucet et al. (2000) Neuroscience 95, 881-892]. As expected from the recognition of functional 5-HT3 receptors, immunostaining by this anti-5-HT3-R-AS antibody matched the distribution of the high-affinity 5-HT3 binding sites in the rat brain and spinal cord. 5-HT3-AS-like immunoreactivity was detected at low levels in the limbic system, particularly in the amygdala and the hippocampus, and in the frontal, piriform and entorhinal cortices. High levels of immunoreactivity were found in the brainstem, mainly in the nucleus tractus solitarius and the nucleus of the spinal tract of the trigeminal nerve, and in the dorsal horn of the spinal cord. At the ultrastructural level, immunostaining was generally found associated with axons and nerve terminals (70-80%) except in the hippocampus, where labelled dendrites were more abundant (56%). This preferential localization on nerve endings is consistent with the well-documented physiological role of 5-HT3 receptors in the control of neurotransmitter release. However, the different distribution in the hippocampus raises the question of whether differential addressing mechanisms exist for preferentially targeting 5-HT3 receptors to postsynaptic dendritic sites as compared to presynaptic nerve endings, depending on the nature of the neurons bearing these receptors.

Serotonin transporter gene polymorphisms and hyperserotonemia in autistic disorder

Previous studies have provided conflicting evidence regarding the association of the serotonin transporter (5-HTT) gene with autism. Two polymorphisms have been identified in the human 5-HTT gene, a VNTR in intron 2 and a functional deletion/insertion in the promoter region (5-HTTLPR) with short and long variants. Positive associations of the 5-HTTLPR polymorphism with autism have been reported by two family-based studies, but one found preferential transmission of the short allele and the other of the long allele. Two subsequent studies failed to find evidence of transmission disequilibrium at the 5-HTTLPR locus. These conflicting results could be due to heterogeneity of clinical samples with regard to serotonin (5-HT) blood levels, which have been found to be elevated in some autistic subjects. Thus, we examined the association of the 5-HTTLPR and VNTR polymorphisms of the 5-HTT gene with autism, and we investigated the relationship between 5-HTT variants and whole-blood 5-HT. The transmission/disequilibrium test (TDT) revealed no linkage disequilibrium at either loci in a sample of 96 families comprising 43 trios and 53 sib pairs. Furthermore, no significant relationship between 5-HT blood levels and 5-HTT gene polymorphisms was found. Our results suggest that the 5-HTT gene is unlikely to play a major role as a susceptibility factor in autism.

Effects of acetaminophen on monoaminergic systems in the rat central nervous system

Although acetaminophen is a well established analgesic, its mechanism of action is still unknown. We investigated whether this drug could affect central monoaminergic neurotransmission in rats. Significant increases in serotonin (5-HT) levels were found in the posterior cortex, hypothalamus, striatum, hippocampus and brain stem, but not spinal cord, 45 min after per os administration of 200-400 mg/kg of acetaminophen. However, this treatment altered neither the levels of 5-hydroxyindoleacetic acid nor the accumulation of 5-hydroxytryptophan after blockade of aromatic L-amino acid decarboxylase. On the other hand, a decrease in both the levels of the dopamine (DA) metabolite, dihydroxyphenylacetic acid, and the accumulation of dihydroxyphenylalanine were noted in the striatum of acetaminophen-treated rats. Finally, acetaminophen administration significantly increased noradrenaline (NA) levels in the posterior cortex. In vitro studies showed that acetaminophen (1 mM) enhanced K+-evoked overflow of [3H]5-HT, but not [3H]DA and [3H]NA, previously taken up in brain slices, and exerted no direct effect on monoamine oxidase A, tyrosine hydroxylase and catechol-O-methyl-transferase activities. These results indicate that acetaminophen affects central monoaminergic neurotransmission, thereby suggesting that monoamines (especially 5-HT) might participate in its analgesic action.

The challenges of conducting clinical research: one research team's experiences

Conducting clinical research is an exciting and a rewarding endeavor. Each project is unique and, because of this uniqueness, research studies require considerable planning. Regardless of all the upfront planning, challenges will occur throughout the life of the study. Clinical research projects are rife with obstacles that range from the lack of administrative and physician support to subject attrition. Some of the challenges, such as subject dropout, are not unexpected, whereas other unanticipated issues can blindside a research team. This case study examines several such challenges experienced in one longitudinal study and presents the solutions engineered by the research team to keep the project on track.

Agonist-induced internalization of serotonin-1a receptors in the dorsal raphe nucleus (autoreceptors) but not hippocampus (heteroreceptors)

Serotonin-1A (5-HT(1A)) receptors in the CNS are a major target for psychotropic drugs. In nucleus raphe dorsalis (NRD) and hippocampus (CA3), the selective 5-HT(1A) agonist (+)-8-hydroxy-2-(di-N-propylamino) tetralin (8-OH-DPAT) reduces the firing activity of serotoninergic (5-HT) and pyramidal neurons, respectively. When located on 5-HT (autoreceptors), but not on non-5-HT (heteroreceptors) neurons, 5-HT(1A) receptors are known to be subject to desensitization. Using quantitative electron microscopy after pre-embedding immunogold labeling with specific antibodies, we examined the subcellular distribution of these receptors after acute administration of 8-OH-DPAT (0.5 mg/kg, i.v.). Silver-intensified immunogold particles associated with the plasma membrane or the cytoplasm were counted in somata and dendrites within the NRD, 15 min, 1 hr and 24 hr after 8-OH-DPAT injection, and in hippocampal dendrites 1 hr after the same treatment. Significant decrease in the density of membrane labeling and concomitant increase of cytoplasmic labeling were demonstrated in the NRD, 15 min and 1 hr after 8-OH-DPAT administration, with a return to baseline level at 24 hr. Internalization was blocked by previous administration of the 5-HT(1A) antagonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl) cyclohexane-carboxamide (WAY 100635), which, by itself, was without apparent effect. In hippocampus (CA3), there were no apparent changes in the distribution of the receptor after 8-OH-DPAT administration. These findings are in line with earlier results showing a desensitization of 5-HT(1A) autoreceptors but not heteroreceptors after treatment with 5-HT(1A) receptor agonist. They suggest that this desensitization is the result of autoreceptor internalization.

Serotonin transporter overexpression is responsible for pulmonary artery smooth muscle hyperplasia in primary pulmonary hypertension

Hyperplasia of pulmonary artery smooth muscle cells (PA-SMCs) is a hallmark pathological feature of primary pulmonary hypertension (PPH). Here we found that PA-SMCs from patients with PPH grow faster than PA-SMCs from controls when stimulated by serotonin or serum and that these effects are due to increased expression of the serotonin transporter (5-HTT), which mediates internalization of indoleamine. In the presence of 5-HTT inhibitors, the growth stimulatory effects of serum and serotonin were markedly reduced and the difference between growth of PA-SMCs from patients and controls was no longer observed. As compared with controls, the expression of 5-HTT was increased in cultured PA-SMCs as well as in platelets and lungs from patients with PPH where it predominated in the media of thickened pulmonary arteries and in onion-bulb lesions. The L-allelic variant of the 5HTT gene promoter, which is associated with 5-HTT overexpression and increased PA-SMC growth, was present in homozygous form in 65% of patients but in only 27% of controls. We conclude that 5-HTT activity plays a key role in the pathogenesis of PA-SMC proliferation in PPH and that a 5HTT polymorphism confers susceptibility to PPH.

5-hydroxytryptamine (5-HT)1A autoreceptor adaptive changes in substance P (neurokinin 1) receptor knock-out mice mimic antidepressant-induced desensitization

Antagonists at substance P receptors of the neurokinin 1 (NK1) type have been shown to represent a novel class of antidepressant drugs, with comparable clinical efficacy to the selective serotonin (5-HT) reuptake inhibitors (SSRIs). Because 5-HT(1A) receptors may be critically involved in the mechanisms of action of SSRIs, we examined whether these receptors could also be affected in a model of whole-life blockade of NK1 receptors, i.e. knock-out mice lacking the latter receptors (NK1-/-). 5-HT(1A) receptor labeling by the selective antagonist radioligand [(3)H]N-[2-[4-(2-methoxyphenyl)1-piperazinyl]-ethyl]-N-(2-pyridinyl)-cyclohexanecarboxamide (WAY 100635) and 5-HT(1A)-dependent [(35)S]GTP-gamma-S binding at the level of the dorsal raphe nucleus (DRN) in brain sections, as well as the concentration of 5-HT(1A) mRNA in the anterior raphe area were significantly reduced (-19 to -46%) in NK1-/- compared with NK1+/+ mice. Furthermore, a approximately 10-fold decrease in the potency of the 5-HT(1A) receptor agonist ipsapirone to inhibit the discharge of serotoninergic neurons in the dorsal raphe nucleus within brainstem slices, and reduced hypothermic response to 8-OH-DPAT, were noted in NK1-/- versus NK1+/+ mice. On the other hand, cortical 5-HT overflow caused by systemic injection of the SSRI paroxetine was four- to sixfold higher in freely moving NK1-/- mutants than in wild-type NK1+/+ mice. Accordingly, the constitutive lack of NK1 receptors appears to be associated with a downregulation/functional desensitization of 5-HT(1A) autoreceptors resembling that induced by chronic treatment with SSRI antidepressants. Double immunocytochemical labeling experiments suggest that such a heteroregulation of 5-HT(1A) autoreceptors in NK1-/- mutants does not reflect the existence of direct NK1-5-HT(1A) receptor interactions in normal mice.

Therapeutic efficacy in experimental polyarthritis of viral-driven enkephalin overproduction in sensory neurons

Rheumatoid arthritis is characterized by erosive inflammation of the joints, new bone proliferation, and ankylosis, leading to severely reduced locomotion and intense chronic pain. In a model of this disease, adjuvant-induced polyarthritis in the rat, neurons involved in pain transmission and control undergo plastic changes, especially at the spinal level. These changes affect notably neurons that contain opioids, such as enkephalins deriving from preproenkephalin A (PA) precursor protein. Using recombinant herpes simplex virus containing rat PA cDNA, we enhanced enkephalin synthesis in sensory neurons of polyarthritic rats. This treatment markedly improved locomotion and reduced hyperalgesia. Furthermore, the progression of bone destruction slowed down, which is the most difficult target to reach in the treatment of patients suffering from arthritis. These data demonstrate the therapeutic efficacy of enkephalin overproduction in a model of systemic inflammatory and painful chronic disorder.

Stimulation of 5-HT2 receptors in the nucleus tractus solitarius enhances NMDA receptor-mediated reflex-evoked bradycardiac responses in the rat

The modulation by 5-HT2 receptors in the nucleus tractus solitarius of the reflex bradycardia evoked by stimulation of peripheral baroreceptors and cardiopulmonary chemoreceptors, and their possible functional interactions with local NMDA receptors, were investigated in pentobarbital- and urethane-anaesthetized rats, respectively. Microinjection of the 5-HT2 receptor agonist, 2,5-dimethoxy-4-iodoamphetamine (0.1-0.5 pmol), into the nucleus tractus solitarius elicited a dose-dependent hypotension and bradycardia. Bilateral microinjections at the same site of a subthreshold dose of 2,5-dimethoxy-4-iodoamphetamine (0.05 pmol) significantly enhanced the aforementioned reflex-evoked bradycardiac responses. In contrast, local bilateral microinjections of the NMDA receptor antagonist, 2-amino-5-phosphonopentanoic acid (500 and 1000 pmol), reduced, in a dose-dependent manner, both reflex-evoked responses. The facilitatory effect of 2,5-dimethoxy-4-iodoamphetamine upon these reflex-evoked bradycardiac responses was prevented by prior local microinjection of low doses of either the selective 5-HT2 receptor antagonist, ketanserin (10 pmol), or 2-amino-5-phosphonopentanoic acid (100 pmol), which, on their own, did not affect the reflex-associated bradycardia. These data suggest that 5-HT2 receptors within the nucleus tractus solitarius participate in a facilitatory modulation of the reflex control of heart rate, probably through functional interactions with local NMDA receptors.

[Ground and first singlet excited dissociation constants of 4-methylumbelliferone: application for indirect spectrofluorimetry of nitriles and nitrosamines]

The light adsorption process provides important changes in the electronic configuration of molecules. For phenolic derivatives, light adsorption contributes to acidity in the excited state. In aqueous medium, excitation of the molecular form (ArOH) undergoes dissociation at the first singlet excited state and subsequent fluorescence emission occurs from the excited ionized form (ArO-*). The emission is higher than from the molecular form and exhibits a shift to the red. The combination of these two phenomena allowed simultaneous increase in selectivity and sensitivity. In addition this method allowed an easy quantification of 4-methylumbelliferone at the nanomolar level and consequently trace levels of nitrates and N-nitrosamines after diazotization and/or denitrozation.

Acetaminophen distribution in the rat central nervous system

Based on the evidence that the antinociceptive effects of acetaminophen could be mediated centrally, tissue distribution of the drug after systemic administration was determined in rat anterior and posterior cortex, striatum, hippocampus, hypothalamus, brain stem, ventral and dorsal spinal cord. In a first study, rats were treated with acetaminophen at 100, 200 or 400 mg/kg per os (p.o.), and drug levels were determined at 15, 45, 120, 240 min by high performance liquid chromatography (HPLC) coupled with electrochemical detection (ED). In a second study, 45 min after i.v. administration of [3H]acetaminophen (43 microCi/rat; 0.65 microg/kg), radioactivity was counted in the same structures, plus the septum, the anterior raphe area and the cerebellum. Both methods showed a homogeneous distribution of acetaminophen in all structures studied. Using the HPLC-ED method, maximal distribution appeared at 45 min. Tissue concentrations of acetaminophen then decreased rapidly except at the dose of 400 mg/kg where levels were still high 240 min after administration, probably because of the saturation of clearance mechanisms. Tissue levels increased with the dose up to 200 mg/kg and then leveled off up to 400 mg/kg. Using the radioactive method, it was found that the tissue/blood ratio was remarkably constant throughout the CNS, ranking from 0.39 in the dorsal spinal cord to 0.46 in the cerebellum. These results, indicative of a massive impregnation of all brain regions, are consistent with a central antinociceptive action of acetaminophen.